For Class: Default: it can be accessed from other classes in the same package and inherited from other classes in the same package. Public: can be accessed and inherited from any class in any package. // Render a class visible to other parts of the program as a whole. It does not represent that all the fields and methods in the class are visible to other parts of the program, the former is a necessary condition for the latter. Whether the domain and method of the class can be accessed (including inheritance) for all other classes depends on the access controllers of these domains and methods. // If the constructor of a class is declared as private, other classes cannot generate an instance of this class. // Although the subtype in different packages can be used to access the members of the parent class limited to protected, the objects accessing these members must have the subclass type or the subclass type, it cannot be a parent class. // Configure //---------------------------------------------------------------------------------------------------------------------
| |
In the same class |
In the same package |
Subclass of different packages |
Non-subclass of different packages |
| Private |
Allow |
|
|
|
| Default |
Allow |
Allowed (subclass and non-subclass) |
|
|
| Protected |
Allow |
Allowed (subclass and non-subclass) |
Allowed (only subclass, and the protected method inherited by subclass cannot be accessed through the subclass instance) |
Unable to access the protedted Method |
| Public |
Allow |
Allowed (subclass and non-subclass) |
Allow |
Allowed (subclass and non-subclass) |
For Class Members:// The Secret subclass can inherit the "default" Domain variables and methods set to public and protected in the parent class, but cannot inherit the domain variables and methods with private access permissions. // ----------------------------- The access modifier and non-access modifier that cannot be used simultaneously: abstract and final cannot simultaneously modify the same class; abstract and private, static, final or native cannot be used together to modify the same method; Private-modified domains and methods cannot be used in abstract classes; abstract methods must exist in abstract classes; the static method cannot process non-static fields. Sample Code: Package pkg1;
Public class country
{
Protected string name;
Protected void value () // friendly
{
Name = "China ";
}
} // ------------------------ Package pkg2;
Import pkg1.country;
Public class main6
{
Public static void main (string [] ARGs)
{
Country C = new country ();
// C. Value (); // Error
}
}
// Sub-classes can inherit the permissions set to public, protedted, and friedly (default) in the parent class.
// Domain variables and methods, but cannot inherit the domain variables and methods with the access permission set to private
Class city extends country
{
Void setvalue ()
{
This. Value (); // correct
Super. Value (); // correct
Country C = new country ();
// C. Value (); // error: the object type accessing the protected member cannot be the parent class.
City cc = New City ();
Cc. Value (); // correct
}
}
